1. Field of the Invention
The present invention relates to an ion implanter for use in connection with a semiconductor substrate. More particularly, the present invention relates to a method for monitoring an ion implanter and ion implanter having a shadow jig for performing the same.
2. Description of the Related Art
Generally, semiconductor devices are manufactured through a three-step process. First, a fabricating process is performed for forming an electrical circuit on a silicon wafer used as a semiconductor substrate. Second, an inspecting process is performed for inspecting electrical characteristics of semiconductor devices formed on the semiconductor substrate. Third, a packaging process is performed for packaging the semiconductor devices in epoxy resins and individuating the semiconductor devices.
The fabricating process may include a film deposition process for forming a specific film on the semiconductor substrate, a chemical and mechanical polishing (CMP) process for planarizing a surface of the film, a photolithography process for forming photoresist patterns on the film, an etching process for forming the film into patterns having the electrical characteristics using the photoresist patterns, an ion implantation process for implanting specific ions into specific portions of the semiconductor substrate, a cleaning process for removing impurities remaining on the semiconductor substrate, an inspecting process for inspecting the film and patterns formed on the semiconductor substrate, or other similar processes.
An ion implantation process is performed to form a source and a drain of a transistor by implanting specific ions into specific portions of a semiconductor substrate. As compared with a thermal diffusing process, the ion implantation process has an advantage in that a dosage of ions implanted into semiconductor substrate and an implantation depth of ions are adjustable.
The specific ions may not be uniformly implanted into semiconductor substrate because of a channeling effect due to a crystal structure of silicon, which composes the semiconductor substrate. Accordingly, the semiconductor substrate should be positioned at a predetermined angle (i.e., tilted) with respect to a direction of an ion beam.
During the ion implantation process, an ion source irradiates an ion beam onto the semiconductor substrate in a horizontal direction, and the semiconductor substrate is tilted at an angle of approximately 7xc2x0 with respect to a vertical plane (xe2x80x9ctilted anglexe2x80x9d). A gate pattern of a transistor formed on the semiconductor substrate and the tilted angle of semiconductor substrate cause a shadow effect on a side portion of the gate pattern.
In order to compensate for this shadow effect, a method of rotating semiconductor substrate by steps during the ion implantation process has been suggested. For example, the ions are primarily implanted into the semiconductor substrate. Then, the semiconductor substrate is rotated by a rotating angle of 180xc2x0 (xe2x80x9crotating anglexe2x80x9d), and the ions are secondarily implanted into the semiconductor substrate.
When the rotation of the semiconductor substrate is not normally performed due to a mechanical failure of the ion implanter, the ion implantation process is repeatedly performed at the same rotating angle. As a result, the shadow is more pronounced on the side portion of the gate pattern, and the shadow causes operational defects and degradation of the transistor.
The shadow is not detected in a typical inspecting process because a width of the shadow is extremely narrow. For example, when a height of the gate pattern is approximately 4500, the width of the shadow is approximately 55 nm. A thermal wave measuring apparatus for a dosage of ions implanted into the semiconductor substrate uses a laser beam having a spot size greater than 1 xcexcm. Accordingly, the thermal wave measuring apparatus cannot detect the shadow. In addition, the shadow cannot be detected in an image analysis process using a scanning electron microscope (SEM) or an ingredient analysis process using a particle analyzing system.
Because the above-mentioned problems cannot be detected immediately after the ion implantation process, the above-mentioned problems are not detected until the operational defects and the degradation of the transistor are observed in the inspecting process for inspecting electrical characteristics of semiconductor devices formed on the semiconductor substrate after the fabricating process. The above-mentioned problems cause a loss of time and materials, and deteriorate the productivity of the semiconductor devices. In addition, because the manufacturing processes of the semiconductor devices are typically performed by the run, the loss corresponding to a rotation error of the semiconductor substrate in the ion implantation process may be multiplied.
In order to overcome at least some of the above-mentioned problems, the present invention provides a method for monitoring an ion implanter, which can monitor whether a rotation of the semiconductor substrate has been normally performed during an ion implantation process.
In addition, the present invention provides an ion implanter having a shadow jig for performing the method for monitoring an ion implanter.
According to an embodiment of the present invention, a method for monitoring an ion implanter includes positioning a substrate behind an interceptor for intercepting a portion of an ion beam to be irradiated toward the substrate, irradiating a first ion beam toward the substrate to form a first shadow on the substrate, rotating the substrate about a central axis of the substrate, irradiating a second ion beam toward the substrate to form a second shadow on the substrate, and measuring a dosage of ions implanted into the substrate to monitor whether the rotation of the substrate has been normally performed.
According to another embodiment of the present invention, a method for monitoring an ion implanter includes interposing an interceptor for intercepting a portion of an ion beam to be irradiated toward a substrate between the substrate and an ion source for irradiating the ion beam, irradiating a first ion beam toward the substrate to form a first shadow on the substrate, rotating the substrate about a central axis of the substrate, irradiating a second ion beam toward the substrate to form a second shadow on the substrate, and measuring a dosage of ions implanted into the substrate to monitor whether the rotation of the substrate has been normally performed.
According to still another embodiment of the present invention, a method for monitoring an ion implanter includes interposing an interceptor for intercepting a portion of an ion beam to be irradiated toward a substrate between the substrate and an ion source for irradiating the ion beam, the substrate being tilted at a predetermined angle with respect to an advancing direction of the ion beam, irradiating a first ion beam toward the substrate to form a first shadow on the substrate, rotating the substrate about a central axis of the substrate with maintenance of the tilted angle, irradiating a second ion beam toward the substrate to form a second shadow on the substrate, measuring a thermal wave value of a surface of the substrate, and comparing a first thermal wave value corresponding to the first shadow with a reference thermal wave value to monitor whether the rotation of the substrate has been normally performed.
Preferably, the ion beam is irradiated toward the substrate in a horizontal direction, and the substrate is tilted at a predetermined angle with respect to an advancing direction of the ion beam.
The dosage of ions implanted into the substrate may be measured using a method of measuring a thermal wave value of a surface of the semiconductor substrate, an image analysis method using a scanning electron microscope, an ingredient analysis method using a particle analyzing system, or an energy analysis method measuring a surface resistance of the semiconductor substrate. Preferably, the dosage of ions implanted into the substrate is measured using a method of measuring a thermal wave value of a surface of the semiconductor substrate.
According to yet another embodiment of the present invention, an ion implanter includes an ion source for irradiating an ion beam toward a substrate, an ion implantation chamber connected to the ion source for performing an ion implantation process on the substrate, a chuck disposed in the ion implantation chamber for supporting the substrate, which is tilted at a predetermined angle with respect to an advancing direction of the ion beam, a first driving unit for rotating the substrate about a central axis of the substrate in order to change an incidence angle of ion beam, and a shadow jig for intercepting a portion of the ion beam in order to form a shadow on the substrate during the ion implantation process, wherein the shadow is formed to monitor whether the substrate has been normally rotated during the ion implantation process.
Preferably, the ion implanter additionally includes a driving unit for adjusting the angle at which the substrate is tilted and a driving unit for moving the chuck in a vertical direction. In addition, the ion implanter preferably includes a driving unit connected to a bracket for moving the shadow jig, wherein the second driving unit moves the shadow jig away from a central portion of the chuck while the substrate is loaded on or unloaded from the chuck, and the second driving unit moves the shadow jig toward a central portion of the chuck for forming the shadow on the substrate during the ion implantation process.
Alternatively, the ion implanter may include a driving unit connected to a bracket for moving the shadow jig, wherein the second driving unit rotates the shadow jig in the vertical direction while the substrate is loaded on or unloaded from the chuck, and the second driving unit rotates the shadow jig back in the horizontal direction for forming the shadow on the substrate during the ion implantation process.
According to the present invention, defects in the ion implantation process caused by a rotation error of the semiconductor substrate can be prevented in advance, and the loss of time and materials can be reduced.